1. Field of the Invention
The present invention relates to a bus bar module integrally composed of bus bar and resin insulating layer.
2. Description of the Related Art
Electric circuits used in an internal combustion engine and in other high temperature environments utilize a bus bar module. A bus bar module has a plurality of bus bars made of a metallic material that has high heat resisting properties (a copper alloy, for example). The bus bars are aligned in parallel, and a plurality of bus bars are integrated by means of insert molding with insulating layers made of resin material (epoxy resin, for example) having heat resisting properties. Thus, the insulating layers insulate the space between the individual bus bars. A bus bar module as described above, is disclosed in the Japanese Unexamined Patent Publication No. 2000-151149.
The thermal expansion coefficient of metal generally differs widely from the thermal expansion coefficient of resin. Thus, there is a fear that repeated cycling from room temperature conditions to high temperature conditions may cause cracks in the resin of a bus bar module that has a metallic bus bar integrated into a resin insulating layer due to the differences of the thermal expansion coefficients.
Accordingly, in view of the aforementioned circumstances, the present invention is originated and the subject of the present invention is to prevent the occurrence of the crack in the resin insulating layer.
The present invention relates to a bus bar module with a bus bar made of a conductive metallic material and an integrally molded resin insulating layer. The bus bar module further includes a distortion absorptive means for absorbing a distortion that results from a difference in thermal expansion coefficients between the bus bar and insulating layer.
The distortion absorptive means preferably is disposed to divide the insulating layer at an appropriate position along the longitudinal direction of the bus bar.
The bus bar module preferably comprises an insulating layer on the surface of the bus bar.
The distortion absorptive means absorbs the distortion that results from a difference in thermal expansion coefficient between the bus bar and the insulating layer. Accordingly, it is possible to prevent cracks from occurring in the insulating layer.
The thermal expansion coefficient of resin is greater than the thermal expansion coefficient of metal. However, the distortion absorptive means at the divided position of the resin layer effectively enables the resin layer to stretch further by the difference in the thermally expanded dimension between the insulating layer and the bus bar. Hence, there would be no possibilities for a forceful deformation and an excessive stress upon the insulating layer.
The bus bar is partially exposed at the divided position of the insulating layer. However, since the surface of the exposed part is covered with an insulating coating, the bus bar can be maintained in an insulating condition.